Fuel Cell System

ABSTRACT

The invention is directed to developing a technique to estimate the remaining time for generating electrical power, which is applicable to small fuel cells used as a power supply in small electronic devices such as mobile phones or portable computers. In a fuel cell system including a fuel cell, a fuel used directly or indirectly for the fuel cell, and a module with internal electrical or physical properties that change as the fuel is used, the present invention is characterized by a method for estimating the remaining time in which the fuel or hydrogen created from the fuel can be provided to the fuel cell, where providing a plurality of electrodes inside the module, measuring electrical or physical properties of the space between at least two of said electrodes, and estimating the remaining time based on the measurement results.

TECHNICAL FIELD

The invention relates to a fuel cell system, and in particular, atechnique to estimate the remaining time that the fuel cell system cangenerate electrical power.

BACKGROUND ART

A fuel cell is a means of generating electrical power via a chemicalreaction of hydrogen or methanol. Although fuel cells are referred to ascells, they may also be referred to as power generators. The features offuel cells are: light environmental load because no carbon dioxide isgenerated through the burning of gases and oils; and great powergenerating efficiency due to the chemical energy of fuel being directlyconverted to electrical energy. Therefore, more expectations have beenplaced on fuel cells as an energy source for the next generation.

Currently, portable fuel cell systems can be broadly classified into twotypes: hydrogen driven and direct methanol. In hydrogen driven fuelcells, hydrogen is directly supplied to a cation-exchange membrane togenerate electrical power. In contrast, in direct methanol fuel cells,electricity is directly obtained through a dehydrogenating hydrogenoxidation reaction of methanol. In hydrogen driven fuel cells, there arewell-known methods for directly storing the hydrogen to be carried asdirect fuel in a tank, with hydrogen being obtained from such carriedforms as hydrogen storage alloy, water, and methanol. In Japanese PatentLaid-Open No. 2003-221201, a technique is disclosed for generatinghydrogen by reacting water and a metal alloy. Additionally, in JapanesePatent Laid-Open No. 2003-306301, a technique is disclosed for obtaininghydrogen from dehydrogenative oxidation of an aromatic compound with acatalyst.

A user needs to know how much longer a fuel cell will generate power, nomatter the kind of portable fuel cell. Without this knowledge, itbecomes inconvenient as an electronic apparatus using the fuel cell as apower source will suddenly stop when the battery is exhausted. When afuel cell is of a type that is placed on the ground and is continuouslysupplied with fuel such as city gas, the abovementioned items are notparticularly problems. Also, when the fuel cell is relatively large suchthat it is used as the power source for a car, a method for estimatingthe remaining time in which the fuel cell can generate electrical power,by installing a fuel indicator or a gas pressure sensor in the fuel tankto measure the remaining fuel may be considered. However, when a fuelcell is used as a power source for a portable or compact electronicapparatus, since the fuel cell itself is required to be compact andinexpensive, it may be inappropriate to install a fuel indicator or apressure sensor therein. Consequently, in conventional fuel cells for aportable electric apparatus, a method in which the remaining fuel ischecked, for example, with the eyes through a window attached on thefuel storage for estimating the remaining time in which the fuel cellcan generate electrical power.

DISCLOSURE OF THE INVENTION

The present invention is directed to developing a technology to estimatethe remaining time for generating electrical power, which is applicableeven to small fuel cells used as a power supply in small electronicdevices such as mobile phones or portable computers.

When viewed from one aspect of the present invention, in a fuel cellsystem comprising a fuel cell, a fuel used directly or indirectly forthe fuel cell, and a module with internal electrical or physicalproperties that change as the fuel is used, the present invention ischaracterized by a method for estimating the remaining time in which thefuel or hydrogen created from the fuel can be provided to the fuel cell,where the method providing a plurality of electrodes inside the module,measuring electrical or physical properties of the space between atleast two of said electrodes, and estimating the remaining time based onthe measurement results.

When the present invention is viewed from another aspect, in a fuel cellsystem comprising a fuel cell, a fuel used directly or indirectly forthe fuel cell, and a module with internal electrical or physicalproperties that change as the fuel is used, the present invention ischaracterized by a method for alerting the user when the remaining timein which the fuel or hydrogen created from the fuel can be provided tothe fuel cell is low, where the method providing a plurality ofelectrodes inside the module, measuring electrical or physicalproperties of the space between at least two of said electrodes, andalerting the user when the measurement results are larger or smallerthan a threshold.

The abovementioned electrical properties may be one or more ofresistance, capacitance, inductance, and impedance. Additionally, theabovementioned physical properties may be one or more of magneticsusceptibility, expansion coefficient, and morphology.

In one embodiment of the present invention, if the abovementioned fuelcell system creates hydrogen by a chemical reaction between theabovementioned fuel and a catalyst for the reaction, the fuel cellsystem may be configured to arrange at least two of the plurality ofelectrodes so that the abovementioned catalyst is located in between thetwo electrodes, in order to measure variations in electrical or physicalproperties of the space between the abovementioned electrodes caused bythe chemical change in the catalyst. Additionally, in another embodimentof the present invention, if the abovementioned fuel cell systemcomprises a fuel storage for storing the abovementioned fuel andprovides the fuel to the fuel cell directly or after a reformulation,the fuel cell system may be configured to arrange at least two of theplurality of electrodes in the fuel storage so that the fuel can belocated between the two electrodes to measure variations in electricalor physical properties, which depend on the amount of fuel remainingbetween the two electrodes. Moreover, in yet another embodiment of thepresent invention, if the abovementioned fuel cell system comprises acasing for storing the abovementioned fuel and a catalyst forreformulating the fuel, the abovementioned electrodes may be located inthe casing.

When the present invention is further viewed from another aspect, thepresent invention is characterized by a fuel cell system comprising apower outlet for providing electrical power for an external device, afuel used directly or indirectly for the fuel cell, a module whoseinternal electrical or physical properties change as the abovementionedfuel is used, two electrodes installed in the module for measuringelectrical properties of the space between the two electrodes, and twoprobe-contacts, each of them being in contact with each of theabovementioned two electrodes electrically, for providing electricalcontact with the two electrodes. The abovementioned electricalproperties may be one or more of resistance, capacitance, inductance,and impedance. Additionally, the abovementioned physical properties maybe one or more of magnetic susceptibility, expansion coefficient, andmorphology.

In one embodiment of the present invention, the abovementionedprobe-contacts may be provided on the abovementioned housing of themodule. And, in some embodiments, the abovementioned power outlets andthe abovementioned probe-contacts are provided on the housing of theabovementioned fuel cell system. Furthermore, in some embodiments, theabovementioned power outlets and the abovementioned probe-contacts formpart of the connector.

In one embodiment of the present invention, the abovementioned fuel cellsystem is characterized by comprising a hydrogen generator for obtaininghydrogen from fuel used for the fuel cell system, wherein theabovementioned two electrodes are installed in the hydrogen generator.In this case, the abovementioned hydrogen generator may further comprisea fuel inlet for receiving the abovementioned fuel from another part ofthe abovementioned fuel cell system, and a hydrogen outlet forexhausting hydrogen generated by the above-mentioned chemical reactionto another part of the fuel cell system.

In one embodiment of the present invention, the abovementioned hydrogengenerator comprises a catalyst for generating hydrogen from the fuelthrough a chemical reaction. In this case, the abovementioned catalystis preferably installed in between the abovementioned two electrodes. Inthis embodiment, one of the abovementioned two electrodes may comprise apart of the outer wall of one side of the hydrogen generator, and theother of the abovementioned two electrodes may comprise a part of theouter wall of the other side of the hydrogen generator, and aninsulator-layer in between the one side and the other side of the outerwall. The inside surface of the outer wall of the abovementionedhydrogen generator may be coated by an insulator-layer. At least one ofthe abovementioned two electrodes may comprise an insulator-layer on thesurface thereof. The abovementioned insulator-layer may be composed ofat least one of the following materials: paper, a polyolefin such aspolyethylene or polypropylene, a polyester such as polyethyleneterephthalate, an aromatic or aliphatic polyamide, a polyurethane, apolyimide, a phenol resin, a liquid crystalline polymer, PPS, an epoxyresin, PEEK, or PES. Furthermore, in this embodiment, the abovementionedhydrogen generator comprises a support member for supporting theabovementioned catalyst for the reaction. The support member may becomposed of one of the following materials: metal, carbon, conductivepolymer, and conductive ceramic. Additionally, the support member mayhave the shape of a net, lattice, or perforations. Moreover, the memberis conductive, and is used as one of said two electrodes. Furthermore,in one embodiment of the present invention, one part of theabovementioned catalyst is mounted on the abovementioned support memberso that one part faces the support member and does not face theabovementioned fuel, and the abovementioned other part of the catalystis mounted on the abovementioned support member so that the other partdirectly contacts with the abovementioned fuel. Additionally, in oneembodiment, the abovementioned catalyst is installed in a removablemanner in the abovementioned hydrogen generator.

In one embodiment of the present invention, the abovementioned hydrogengenerator comprises a catalyst to accelerate a hydrogen generatingreaction in which the hydrogen is created by a change in the fuelitself. One of the abovementioned two electrodes may comprise a part ofan outer wall of the abovementioned hydrogen generator. One of the twoelectrodes comprises a part of an outer wall of one side of theabovementioned hydrogen generator, and the other of the abovementionedtwo electrodes comprises a part of an outer wall of the other side ofthe abovementioned hydrogen generator, and an insulator-layer is formedin between the one side and the other side of the abovementioned outerwall. At least one of the abovementioned two electrodes comprises aninsulator-layer on the surface thereof, and the insulator-layer iscomposed of at least one of the following materials: paper, a polyolefinsuch as polyethylene or polypropylene, a polyester such as polyethyleneterephthalate, an aromatic or aliphatic polyamide, a polyurethane, apolyimide, a phenol resin, a liquid crystalline polymer, PPS, an epoxyresin, PEEK, and PES. Furthermore, in some embodiments, theabovementioned catalyst has the shape of a lattice and/or is perforated.Additionally, the abovementioned hydrogen generator is attached in aremovable manner to another part of the hydrogen generator fuel cellsystem.

In one embodiment of the present invention, the abovementioned fuel cellsystem may comprise a casing for storing the fuel to be used for thesystem, wherein said plurality of electrodes are installed in thecasing. Also, in this case, one of the abovementioned two electrodescomprises a part of an outer wall of the abovementioned casing.Furthermore, one of the abovementioned two electrodes comprises a partof an outer wall of one side of the abovementioned casing, and the otherof the abovementioned two electrodes comprises a part of an outer wallof the other side of the abovementioned casing, and an insulator-layeris formed in between the one side and the other side of theabovementioned outer wall. If at least one of the abovementioned twoelectrodes comprises an insulator-layer on the surface thereof, theinsulator-layer is composed of at least one of the following materials:paper, a polyolefin such as polyethylene or polypropylene, a polyestersuch as polyethylene terephthalate, an aromatic or aliphatic polyamide,a polyurethane, polyimide, a phenol resin, a liquid crystalline polymer,PPS, an epoxy resin, PEEK, and PES. Moreover, in the embodiments, theabovementioned casing comprises a holding material to hold theabovementioned fuel in, and a support member to support the holdingmaterial. In this case, the abovementioned support member preferably hasthe shape of a net, lattice, or is perforated. Furthermore, theabovementioned support member is conductive, which is preferably used asone of the abovementioned two electrodes. The abovementioned casing maybe attached in a removable manner to another part of the abovementionedfuel cell.

In one embodiment of the present invention, the fuel cell systemaccording to the present invention is portable.

When the present invention is viewed from another aspect, the presentinvention includes a device comprising main probe-contacts forelectrically connecting with said probe-contacts, used together with afuel cell system by the present invention disclosed above, and a powerinlet for electrically connecting with said power outlets. In oneembodiment, the abovementioned power inlets and the abovementioned mainprobe-contacts may be included in a connector.

When the present invention is viewed from another aspect, the presentinvention comprises a device comprising a measuring instrument forconnecting to the abovementioned probe-contacts, used together with afuel cell system by the present invention disclosed above, and measuringelectrical and/or physical properties in between the two electrodes, andan estimator for estimating the remaining time in which the fuel cellcan produce electrical power, based on the measurement results.Furthermore, when the present invention is viewed from another aspect,the present invention comprises a fuel cell system by the presentinvention disclosed above, a measuring instrument for connecting to theabovementioned probe-contacts and measuring electrical and/or physicalproperties in between the abovementioned two electrodes, and anestimator for estimating the remaining time in which the fuel cell canproduce electrical power based on the measurement results. In oneembodiment, the abovementioned estimator may be configured to produce analert for the user if the apparatus estimates that the remaining time inwhich the fuel cell can produce electrical power is short. And theabovementioned estimator may be configured to shut down the apparatus ifthe apparatus estimates that the remaining time in which the fuel cellcan produce electrical power is short. Moreover, in one embodiment, theapparatus by the present invention is portable, and in particular, amobile phone.

The present invention can make it possible to estimate the remainingtime in which the fuel cell can produce electrical power, regardingsmall fuel cells, used as the power supply in small electronic apparatussuch as mobile phones or portable computers, as well as large fuelcells.

MOST PREFERABLE EMBODIMENTS FOR IMPLEMENTING THE INVENTION

The embodiments for carrying out the invention are described withreference to the attached drawings below. FIG. 1 is an outline of thefuel cell system according to the invention. A fuel cell system 2according to the invention comprises a fuel cell 4, a measuringinstrument 6 and an estimator 8. The fuel cell 4 comprises an electrodeinstallation section 10 and a fuel cell 12. The electrode installationsection 10 comprises an electrode 14 and an electrode 16, and alsostores various fuel and catalysts depending on the type of the fuel cell4, and the electrodes 14 and 16 are placed such that the fuel and thecatalysts exist in a space 18 between these electrodes. Each of theelectrodes 14 and 16 are electrically connected by probe-contacts 20, 22on the housing of the fuel cell 12. The fuel cell 12 is the section toproducing electrical power from a chemical reaction, which may obtainelectrical power from the binding reaction of hydrogen and oxygen or mayobtain electrical power through the oxidation reaction of methanol. Theproduced electrical power is supplied to the whole fuel cell system 2from power outlet 24 provided on the housing of the fuel cell 4. Themeasuring instrument 6 is connected with the electrodes 14, 16 throughthe probe-contacts 20, 22, which comprises the estimator to for estimateestimating electrical properties such as resistance, capacitance andimpedance between these electrodes. Estimator 8 controls the estimator6, causing the estimator 6 to measure electrical properties between theelectrodes 14 and 16. As the fuel cell 4 continues producing electricalpower, the amount of fuel, chemical properties of the fuel or chemicalproperties of the catalyst are changed existing in the interval space 18between the electrode 14 and 16 are changed. Therefore, as the fuel cell4 continues producing electrical power, the electric resistance,capacitance and dielectric constant in the space 18 are changed. If ameasuring instrument such as a resistance meter or impedance measuringequipment is connected to the probe-contacts 20, 22 to measure electricresistance, capacitance and impedance between the electrodes 14 and 16over time, the change in electrical properties/physical properties inthe space 18 arising from the continuing electrical generation can becaptured. The estimator 8 controls the measuring instrument 6 in thetaking of measurements over time and receives the measurement valuesfrom the measuring instrument 6 over time. Further, the estimator 8estimates, from the change in the received measurement values, theremaining time for supplying fuel or hydrogen produced by the fuel tothe fuel cell 12. This remaining time directly relates to the remainingtime for producing electrical power of the fuel cell 4, which means theestimator 8 estimates the time for producing electrical power for thefuel cell 4.

What is changed by continuing electrical generation depends on the typeof fuel cell. The electrodes mentioned above are preferably installed ina place where they can capture changes most easily, according to thetype of fuel cell. For example, in the case of fuel cells in whichhydrogen is obtained by reacting water and a catalyst (catalytic metal)and electrical power is produced by reacting hydrogen and oxygen, theelectrodes can even be installed where the catalyst is installed becausethe catalyst is oxidized with time and the electric and physicalproperties are changed. Additionally, in direct methanol fuel cells, theelectrodes should be installed in the fuel storage because methanol isreduced over time. More specific embodiments of a fuel cell in which theinvention is applied are described below, with the preferred electrodestructure.

How accurately the estimator 8 can estimate the remaining time toproduce electrical power in a fuel cell depends on what is changed bycontinuing electrical generation, as well as the shape of theelectrodes, structure and installation method. However, at least whenthe measurement values received from the measuring instrument 6 arelarger than a threshold or smaller than a predetermined threshold, theestimator 8 can estimate that the remaining time for producingelectrical power is short. If the remaining time for producingelectrical power is short, the fuel cell system 2 is preferablyconfigured to alert the user of the fuel cell system 2 accordingly andto shut down the power of the fuel cell system 2.

FIG. 2 is an embodiment in which the fuel cell system according to theinvention is applied to a mobile phone. FIG. 2 shows a mobile phoneusing the fuel cell system according to the invention. Mobile phone 30comprises display 32, on-hook key 34, off-hook key 36, function keys 38,number keys, 40 and fuel cell 42. The fuel cell 42 is similar to thefuel cell 4 in FIG. 1. As shown in FIG. 2 (b), the fuel cell 42 can beseparated from the main body of the mobile phone 30. The contact surfaceof the fuel cell 42 with the main body of the mobile phone 30 comprisesthe power outlets 48 (equivalent to the power outlets of the fuel cell 4in FIG. 1) for providing electrical power produced by the fuel cell 42to the main body of the mobile phone 30, and the probe-contacts 50,equivalent to the probe-contacts 20, 22 of the fuel cell 4 in FIG. 1. Inother words, the probe-contacts 50 provide electrical contact with theelectrodes installed in the inside of the fuel cell 42, which isequivalent to the electrodes 14, 16 of the fuel cell 4 in FIG. 1. Andthe contact surface of the main body of the mobile phone 30 comprisesthe power inlets 44 receiving electrical power from the power outlets 48of the fuel cell 42, and the main probe-contacts 46, which areelectrically connected to the probe-contacts 50. The mobile phone 30estimates a the remaining time to for produce producing electrical powerof the fuel cell 42 by measuring electrical properties betweenelectrodes equivalent to the electrodes 14, 16 of the fuel cell 4 inFIG. 1, which is are installed in the inside of the fuel cell 42,through the main probe-contacts and the probe-contacts 50 of the fuelcell 42.

Additionally, in FIG. 2, the power outlets 48 and the probe-contacts 50are provided on the housing of the fuel cell 42, and can be provided inone connector. Furthermore, the main body of the mobile phone 30 maycomprise the connector, gathering together the power inlet 44 and themain probe-contacts 46. From the above, standardization of the connectorconnecting the fuel cell and the electronic apparatus, which comprisesthe power outlets and the probe-contacts, including its configuration,has a cost advantage as well as the configuration.

FIG. 3 is an outline of the hardware structure of the mobile phone 30.The mobile phone 30 comprises a CPU 54, which connects to a baseband LSI56, a keypad 60, a display 32, a RAM 64 and a ROM 66. The baseband LSI56 is connected to an RF circuit 57, and furthermore the RF circuit 57is connected to an antenna 58. The keypad 60 includes an on-hook key 34,an off-hook key 36, function keys 38 and number keys 40, as shown inFIG. 2. In the ROM 66, are stored programs in which the CPU 54 controlsfunctions of the mobile phone 30.

Furthermore, the CPU 54 connects to a measuring instrument 68, which isequivalent to the measuring instrument 6 in FIG. 1. The measuringinstrument 68 is electrically connected to the fuel cell 42 through themain probe-contacts 46 and the probe-contacts 50 on the fuel cell, asshown in FIG. 2. According to the programs stored in the ROM 66, the CPU54 makes the measuring instrument 68 to check electrical properties(resistance, capacitance, etc.) over time between the electrodes,equivalent to the electrodes 14, 16 in FIG. 1, which are installed inthe inside of the fuel cell 42 over time, and receives the measurementvalues. Additionally, according to the programs stored in the ROM 66,the CPU 54 estimates the remaining time for producing electrical powerof the fuel cell 42 from the measurement values. The results of theestimate are shown on the display 32 and presented to the user of themobile phone 30. Furthermore, according to the programs stored in theROM 66, if the measurement values are larger than a threshold (orsmaller), the CPU 54 disables specific functions of the mobile phone 30or shuts down the power of the mobile phone 30. Thus, the estimator 8works according to the CPU 54 and the programs stored in the ROM 66.

Next, more specific embodiments of the fuel cell to which the inventionis applied are described, with preferable configurations, in thefollowing embodiments.

Example 1

Example 1 illustrates an example of applying the invention to fuel cellsin which hydrogen is obtained by the reaction of a hydrogen supply bodysuch as methanol or water with a catalyst and then generatingelectricity by a reaction of the obtained hydrogen with oxygen. In thistype of fuel cell, the catalyst itself is oxidized by a chemicalreaction with the hydrogen supply body. Wherein, a “metal catalyst” isused in Japanese Patent Laid-Open No. 2003-221201 referenced in thesection, Background of the Art.

FIG. 4 is an outline of the fuel cell system applying the invention inthe example. A fuel cell 70 comprises a fuel tank 72, a hydrogengenerator 74, a power generator 76, a power outlet 78, and aprobe-contact 80. Fuel such as water or alcohol is stored in the fueltank 72. The hydrogen generator 74 comprises a catalyst to generatehydrogen in a chemical reaction between the fuel supplied from the fueltank and the catalyst. To capture the chemical change in the catalystundergoing this chemical reaction, electrodes corresponding to theelectrode 14 and 16 in FIG. 1 are installed in the hydrogen generator74. The probe-contact 80 supplies an electrical contact with theseelectrodes, and corresponds to the probe-contacts 20, 22 in FIG. 1. Thepower generator 76 comprises a fuel cell that generates electricity by achemical reaction of hydrogen supplied from the hydrogen generator 74with externally taken oxygen. Generated electricity is suppliedexternally from the power outlet 78. The power outlet 78 corresponds tothe power outlet 24 in FIG. 1.

The catalyst used in the example is required for generating hydrogen ina chemical reaction with a hydrogen supply body such as water oralcohol. For example, metalic catalysts include nickel and its alloys,iron and its alloys, vanadium and its alloys, manganese and its alloys,titanium and its alloys, copper and its alloys, silver and its alloys,calcium and its alloys, zinc and its alloy, zirconium and its alloys,cobalt and its alloys, chrome and its alloys, aluminium and its alloys,and so on. Aluminum generates hydrogen by reacting with water at hightemperatures, and aluminum itself becomes aluminum oxide. Taking intoconsideration safety and ease of control, it is preferable to use zincand its alloys or transition materials of zinc and its alloys. That is,it is preferable to use nickel, iron, vanadium, manganese, titanium,copper, silver, zirconium, cobalt, chrome and their respective alloys.The surface area of the catalyst can be expanded by being installed inthe hydrogen generator 74 in granular form.

FIG. 5 is a drawing showing the installation mode of the electrode andthe catalyst which are installed in the hydrogen generator 74. FIG. 5(a) shows the simplest embodiment, wherein electrodes 84 and 86 areinstalled such that the catalyst 88 is placed between them. It showsthat, when fuel such as water or alcohol enters from the left side ofthe drawing, a chemical reaction with the catalyst 88 results, uponwhich hydrogen is generated and emitted from the right side of thedrawing. As the reaction continues, the electric resistance of thecatalyst 88 is increased due to the catalyst 88 being oxidized in thischemical reaction. Such changes in electrical properties can be measuredby connecting a resistance meter or impedance measuring equipment to theelectrodes 84, 86. Probe-contacts 80 in FIG. 4 provide electricalcontact between electrodes 84, 86 and the exterior of the fuel cell 70.

In the embodiment shown in FIG. 5 (b), insulator-layers 90, 92 areinstalled between the electrodes 84, 86 and the catalyst 88. Thin paper,nonwoven fabric, macromolecule film, and on the like can be used as aninsulator. In addition, the oxidized catalyst also acts as aninsulator-layer. Said insulator-layer prevents unnecessary chemicalreaction with the fuel and contributes to the stability of the hydrogengenerator 74.

In the embodiment shown in FIG. 5 (c), a support member 93 supportingthe catalyst 88 is installed between the electrode 86 and the catalyst88. Since the support member 93 decreases unnecessary movement of thecatalyst 88, the electrical properties between electrodes 84, 86 may bemeasured more stably. Stabilizing the catalyst 88 is particularlyimportant when the fuel cell is carried and used. An organic orinorganic binder or a method such as a sintering can be used to bond thecatalyst 88 to the support member 93. A conductive material such asmetal, carbon, conductive polymer, conductive ceramics, may be used forthe support member 93. Naturally, a nonconductive material may also beused. Furthermore, the support member 93 may be formed such that it hasa sponge-like or a fabric-like structure, an activated carbon-likestructure, or a perforation structure in order to expand its surfacearea. When the support member 93 has conductivity, it can also be usedinstead of the electrode 86.

In the embodiment shown in FIG. 5 (d), an insulator-layer 94 isinstalled between the support member 93 and the catalyst 88 to avoidunnecessary interaction between the support member 93 and the catalyst88. For the insulator-layer 94, it is preferable to use a material thatis stable under high temperatures such as polyimide resin, PPS, epoxyresin, PEEK, or metal oxide.

In the embodiment shown in FIG. 5 (e), an insulator-layer 95 is furtherinstalled between the catalyst 88 and the electrode 84. The samematerials as for the insulator-layer 94 can be used for theinsulator-layer 95. In such an embodiment, there is an advantage in thatthe corrosion resistance of the electrode can be improved.

The electrodes 84 and 86 are installed to measure electrical propertiessuch as the resistance and the capacitance between the electrodes usingmeasuring equipment which is electrically connected through theprobe-contact 80. A resistance meter or impedance measuring equipmentcan be used as the measuring equipment. The electrodes 84, 86 can takevarious shapes such as mesh or wire in addition to the sheet shape shownin FIG. 5, and an embodiment such that the support member 93 serves asthe electrode 84 or 86 may be considered.

In the embodiment shown in FIG. 6 (a), a gap 96 is provided between thecatalyst 88 and the insulator-layer 95 so that fuel flows into the gap96. The surface opposite the surface facing the gap 96 of the catalyst88 is attached such that it contacts the insulator-layer 94 of thesupport member 93 but does not contact the fuel. In such an embodiment,since it is considered that a portion of the catalyst 88 that isoxidized by the chemical reaction of the catalyst 88 and fuel is formedlaminarly from the surface facing the gap 96 as indicated in referencenumber 98, modest changes in the capacitance between the electrodesresulting from the progress of the chemical reaction can be expected,and therefore, the remaining time in which the fuel cell 70 can generateelectrical power can easily be estimated.

In the embodiment in which a gap is provided between the catalyst andelectrode as shown in FIG. 6 (a), capacitance is suitable as theelectrical property to be measured between the electrodes. Assuming thatan alloy catalyst with a thickness of 10 micrometers is sandwichedbetween two of the electrodes with a gap of 1 micrometer, thecapacitance in the initial state is on the order 10 pF. If the catalystis oxidized for 5 micrometers and the dielectric constant of theoxidized catalyst is around 5, the capacitance at that time will be 5pF.

FIG. 7 (a) is an example of resistance being measured as the electricalproperty between the electrodes. A conductive catalyst 100 is sandwichedbetween the electrode 84 and the electrode 86. Although the catalyst 100may be of the same material as the catalyst 88, it is preferable thatthe shape of the catalyst 100 be cylindrical as shown in FIG. 7 (a) orgranular. In the initial state, the resistance between the electrode 84and the electrode 86 is minimal. For example, a cylinder having a radiusof 10 nm and a height of 1 mm has a resistance on the order of 1mega-ohm. However, as the hydrogen generation reaction between thecatalyst and fuel progresses, the catalyst is oxidized from its surface,and the cross-sectional area of the conductive portion graduallydecreases. Therefore, as the hydrogen generation reaction progresses,the resistance between the electrode 84 and the electrode 86 graduallyincreases. The actual rate of increase of the resistance depends on thematerial used and the shape of the catalyst and electrode.

FIG. 8 is one example of an embodiment of the hydrogen generator 74. Thehydrogen generator 104 in the example comprises an upper housing 104 anda lower housing 105, with a catalyst stored inside. An electrodecorresponding to the electrode 84 shown in FIG. 5 is installed in theupper housing 104, while an electrode corresponding to the electrode 86is installed in the lower housing 105. The upper housing 104 and thelower housing 105 are insulated with a gasket 114. Furthermore, thehydrogen generator 104 comprises a fuel inlet 110 for receiving fuelthat is reacted with the catalyst 108 and a hydrogen outlet 112 forexhausting hydrogen. The inner surface of the upper housing 104 andlower housing 105 may be provided with an insulator-layer. An electrode(not shown) installed in the upper housing 104 and lower housing 105 iselectrically connected to the probe-contact 80 (FIG. 4), respectively.

FIG. 9 is another example of the hydrogen generator 74. The hydrogengenerator 120 in the example comprises a metal housing 121 coveringentire hydrogen generator 120, a fuel inlet 122, and a hydrogen outlet124 both shown in FIG. 8. The metal housing 121 serves as the electrode84 shown in FIG. 5. The inner surface of the metal housing is covered byan insulator-layer 126 corresponding to the insulator-layer 95 in FIG.5. In addition, a support member 128 formed with metal mesh is installedinside the housing, and a catalyst 130 is maintained within the mesh ofthe support member 128. The support member 128 serves as both thesupport member 93 shown in FIG. 5 and the electrode 86 shown in FIG. 5.The surface of the support member 128 is covered by an insulator-layer132. A gasket 134 is provided in the housing 121, and a conductive wire136 which is electrically connected to the support member 128 extends tothe outside of the housing 121 through the gasket 134. The electricalcontact between the support member 128 and the outside can be securedwith this conductive wire 136. The conductive wire 136 is connected tothe probe-contact 80 (FIG. 4), and similarly, the metal housing 121 alsohas electrical contact with the probe-contact 80 (FIG. 4).

As shown in the example, when the catalyst is maintained with a netsupport member, the change in the resistance and capacitance caused bythe movement of the catalyst inside the hydrogen generator 120 at thetime of carrying can be restrained, and thus, the change in theresistance and capacitance caused by oxidation of the catalyst 130 canbe detected more accurately. Therefore, such an embodiment may beadvantageous when the fuel cell according to the invention is used asthe power of a portable electronic apparatus which is always carried andused.

However, since the type of fuel cell described in Example 1 cannot beused because the catalyst is oxidized as hydrogen generation reactioncontinues, it is preferable that the catalyst be configured to bereplaceable. It may be configured such that only the catalyst isreplaceable in the hydrogen generator shown in FIG. 4, or the fuel cell70 may be configured so that all of the hydrogen generator 74 isreplaceable. Naturally, it is necessarily configured to be able torefill with fuel.

Example 2

Example 2 illustrates an example of applying the invention to the typeof fuel cell in which hydrogen is obtained by decomposing fuel which isa hydrogen supply body with a catalyst. The catalyst used in this typeof fuel cell is different from the catalyst in the type of fuel celldescribed in Example 1 in that the catalyst itself is not changed in thehydrogen generation reaction. Hexane and its derivatives, decane and itsderivatives, and so on can be used as fuels which are a hydrogen supplybody. These fuels generate hydrogen via a chemical reaction which isaccelerated by a catalyst. Such catalysts may be composed of materialssuch as nickel, palladium, platinum, rhodium, ruthenium, molybdenum,rhenium, tungsten, vanadium, osmium, chrome, cobalt, and iron.

FIG. 10 is an outline of such a fuel cell system. A fuel cell 140comprises a fuel tank 142, a hydrogen generator 144, a power generator146, a power outlet 148, and a probe-contact 150. Fuel such as hexane ordecane is stored in the fuel tank 142. The hydrogen generator 144comprises a catalyst made of the abovementioned materials, and is filledwith fuel supplied from the fuel tank. Under conditions such as thetemperature becoming sufficiently high, the reaction generates hydrogenfrom the fuel by the action of the catalyst, and the generated hydrogenis supplied to the generator 146. As the hydrogen generation reactioncontinues, since oxidized fuel is increased in the hydrogen generator144, the dielectric constant of the liquid existing in the hydrogengenerator 144 is changed. To detect this change, electrodescorresponding to the electrodes 14, 16 in FIG. 1 are installed in thehydrogen generator 144. The probe-contact 150 provides electricalcontact with these electrodes, and corresponds to the probe-contacts 20,22 in FIG. 1. By connecting a resistance meter, impedance measuringequipment, and on the like to the probe-contact 150 to measureresistance, capacitance, etc. in the hydrogen generator, the remainingtime in which the fuel cell 140 can generate electrical power can beestimated.

The power generator 146 comprises a cell that generates electricity viaa chemical reaction of hydrogen supplied from the hydrogen generator 144and oxygen obtained externally. Generated electricity is suppliedexternally from the power outlet 148. The power outlet 148 correspondsto the power outlet 24 in FIG. 1.

The electrodes installed in the hydrogen generator 144 are installedsuch that fuel is present between them. The surface of the electrodesmay be formed with an insulator-layer. In addition, the catalyst may beone side of the electrode, or the housing of the hydrogen generator 144may be a part of the electrode. FIG. 11 is one example of the hydrogengenerator 144. The hydrogen generator 152 in the example comprises ametal housing 154 covering the entire hydrogen generator 152, a fuelinlet 158, and a hydrogen outlet 160. The inner surface of the metalhousing 154 is covered by an insulator-layer 156. Furthermore, amesh-shaped metal catalyst 155 is installed inside the metal housing.The metal housing 154 and the metal catalyst 155 serve as the electrode14, 16 in FIG. 1, respectively. The housing 154 is provided with agasket 162, and conductive wire 164 which is electrically connected tothe metal catalyst 155 extends outside the housing 154 through thegasket 162. Electrical contact between the metal catalyst 155 and theoutside can be secured with this conductive wire 164.

Example 3

Example 3 illustrates an example of applying the invention to directmethanol fuel cells. Since this type of fuel cell obtains electricity bydecomposing methanol with the fuel electrode of a power generator 176, ahydrogen generator is not required unlike the type of fuel celldescribed in Example 1 and Example 2. When the invention is applied tothis type of fuel cell, electrodes may be installed so that the increasein resistance and decrease in capacitance caused by the decrease in theremaining amount of methanol fuel can be measured.

FIG. 12 is an outline of such a fuel cell system. A fuel cell 170comprises a fuel tank 172, a reservoir tank 174, a power generator 176,a power outlet 178, and a probe-contact 180. The fuel tank 172 is areplaceable cartridge type and methanol fuel is stored therein. Thereservoir tank 174 receives methanol from the fuel tank 172 totemporarily store and then supply it to the power generator 176. Indirect methanol fuel cells, since methanol is consumed while generatingpower, methanol in the reservoir tank 174 decreases gradually after themethanol to be stored in the fuel tank 172 is completely consumed. Sincethe dielectric constant of methanol is large compared to air, thecapacitance of the reservoir tank 174 decreases when methanol decreases.To detect this change, electrodes corresponding to the electrodes 14, 16in FIG. 1 are installed in the reservoir tank 174 by sandwiching fuelbetween them. The probe-contact 180 provides electrical contact withthese electrodes, corresponding to the probe-contacts 20, 22 in FIG. 1.By connecting a measuring instrument corresponding to the measuringinstrument 6 in FIG. 1 to the probe-contact 180 to measure thecapacitance between the electrodes installed in the reservoir tank 174,the remaining time in which the fuel cell 170 can generate electricalpower can be estimated. Electricity generated by the power generator 176is supplied externally from the power outlet 178. The power outlet 178corresponds to the power outlet 24 in FIG. 1.

FIG. 13 is one example of the reservoir tank 174. The reservoir tank 192comprises a metal housing 184 covering the entire reservoir tank 192, afuel inlet 196, and a hydrogen outlet 198. The inner surface of themetal housing 184 is covered with an insulator-layer 186. Furthermore, amesh-shaped conductive support member 188 is installed inside thehousing. The fuel holding material 190 is supported in the net of thesupport member 188. The surface of the support member 188 is insulatedby an insulator-layer 192. The housing 184 and the support member 188serve as the electrodes 14, 16 in FIG. 1, respectively. The housing 184is provided with a gasket 194, and conductive wire 196 which iselectrically connected to the support member 188 extends outside thehousing 184 through the gasket 194. Electrical contact between thesupport member 188 and the outside can be secured with this conductivewire 196. Since the fuel holding material 190 is used to hold fuelinside, porous material such as a sponge is preferable. Since methanolis absorbed in the fuel holding material 190, it can prevent methanolfrom shaking in the reservoir tank 192, and therefore, measuringelectrical properties in the reservoir tank 192 with the housing 184 andthe support member 188 can be performed stably. Therefore, such anembodiment may be advantageous when the fuel cell according to theinvention is used as a power source of a portable electronic apparatuswhich is always carried and used.

Although examples of the present invention have been described above,the above description is illustrative only, and does not limit theembodiment of the invention. For example, electrodes corresponding tothe electrode 14 and 16 may be installed in the fuel tank rather thanthe hydrogen generating part or the reservoir tank. As described above,the present invention can take various modes without departing from thescope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an outline of the fuel cell system according to the invention.

FIG. 2 is an example in which the fuel cell system according to theinvention is applied to a mobile phone.

FIG. 3 is a drawing explaining the hardware configuration of a mobilephone in FIG. 2.

FIG. 4 is an outline of the fuel cell system to which the invention isapplied. (Example 1)

FIG. 5 is a drawing explaining an installation mode of an electrode anda catalyst. (Example 1)

FIG. 6 is a drawing explaining another installation mode of an electrodeand a catalyst. (Example 1).

FIG. 7 is a drawing explaining still another installation mode of anelectrode and a catalyst. (Example 1)

FIG. 8 is a drawing explaining an installation mode of an electrode anda catalyst. (Example 1)

FIG. 9 is a drawing explaining an installation mode of an electrode anda catalyst. (Example 1)

FIG. 10 is an outline of the fuel cell system to which the invention isapplied. (Example 2)

FIG. 11 is a drawing explaining an installation mode of an electrode anda catalyst. (Example 2)

FIG. 12 is an outline of the fuel cell system to which the invention isapplied. (Example 3)

FIG. 13 is a drawing explaining an installation mode of an electrode anda catalyst. (Example 3)

1. For a fuel cell system comprising a fuel cell and a module whoseinternal electrical or physical properties change as fuel is used, amethod for estimating a remaining time in which fuel or hydrogen createdfrom the fuel can be provided to the fuel cell, the method comprisingthe steps of: providing a plurality of electrodes inside of the module,measuring an electrical or a physical property of a space between atleast two of said electrodes, and estimating the remaining time based ona result of the measuring, and wherein the electrical property is one ormore of a resistance, capacitance, inductance, and impedance, andwherein, the fuel cell system can create hydrogen by a chemical reactionof the fuel and a reactive catalyst, the method further comprising:arranging at least two of the plurality of electrodes so that thecatalyst is located in between the two electrode, and measuring avariation of an electrical or a physical property of a space between theelectrodes caused by a chemical change of the catalyst.
 2. For a fuelcell system comprising a fuel cell and a module whose internalelectrical or physical properties change as the fuel is used, a methodfor alerting when a remaining time in which fuel or hydrogen createdfrom the fuel can be provided to the fuel cell becomes low, the methodcharacterized by comprising the steps of: providing a plurality ofelectrodes inside of the module, measuring an electrical or a physicalproperty of a space between at least two of said electrodes, andalerting when a result of the measuring is larger or smaller than athreshold. and wherein the electrical property is one or more of aresistance, capacitance, inductance, and impedance, and wherein, thefuel cell system can create hydrogen by a chemical reaction of the fueland a reactive catalyst, the method further comprising: arranging atleast two of the plurality of electrodes so that the catalyst is locatedin between the two electrode, and measuring a variation of an electricalor a physical property of a space between the electrodes caused by achemical change of the catalyst.
 3. A fuel cell system comprising: apower outlet for providing electrical power for an external device, amodule whose internal electrical or physical property being changed asfuel is used, two electrodes installed in the module, for measuring anelectrical property of a space between the two electrodes, twoprobe-contacts, each of them being contacted with each of the twoelectrodes electrically, for providing electrical contact with the twoelectrodes, and a hydrogen generator for obtaining a hydrogen from fuelused for the fuel cell system, wherein the two electrodes are installedin the hydrogen generator, and the hydrogen generator comprises areactive catalyst for generating hydrogen from the fuel through achemical reaction.
 4. A system according to claim 3, wherein thecatalyst is installed in between the two electrodes.
 5. A systemaccording to claim 3, wherein one of the two electrodes is comprised bya part of an outer wall of the hydrogen generator.
 6. A system accordingto claim 3, wherein one of the two electrodes is comprised by a part ofan outer wall of one side of the hydrogen generator, and the other ofthe two electrodes is comprised by a part of an outer wall of the otherside of the hydrogen generator, and comprising an insulator-layer inbetween the one side and the other side of the outer wall.
 7. A systemaccording to claim 3, wherein at least one of the two electrodescomprises an insulator-layer on the surface thereof.
 8. A systemaccording to claim 7, wherein the insulator-layer is comprised by atleast one of the paper, polyolefin such as polyethylene orpolypropylene, polyester such as polyethylene terephthalate, aromatic oraliphatic polyamide, polyurethane, polyimide, phenol resin, liquidcrystalline polymer, PPS, epoxy resin, PEEK, and PES.
 9. A systemaccording to claim 3, wherein the hydrogen generator comprising asupport member for supporting the catalyst for the reaction, the supportmember is conductive, and is used as one of said two electrodes.
 10. Asystem according to claim 9, wherein the support member is comprised byone of the metal, carbon, conductive polymer, and conductive ceramics.11. A system according to claim 9, wherein the support member has ashape of net, lattice, or porousness.
 12. A system according to claim 9,wherein one part of the catalyst is mounted on the support member sothat the one part faces to the support member and does not face thefuel, and the other part of the catalyst is mounted on the supportmember so that the other part directly contacts with the fuel.
 13. Afuel cell system comprising: a power outlet for providing electricalpower for an external device, a module whose internal electrical orphysical property being changed as fuel is used, two electrodesinstalled in the module, for measuring an electrical property of a spacebetween the two electrodes, two probe-contacts, each of them beingcontacted with each of the two electrodes electrically, for providingelectrical contact with the two electrodes, and a hydrogen generator forobtaining a hydrogen from fuel used for the fuel cell system, whereinthe two electrodes are installed in the hydrogen generator, and thehydrogen generator comprises a catalyst to accelerate a hydrogengenerating reaction in which the hydrogen is created by the change ofthe fuel itself.
 14. A system according to claim 13, wherein one of thetwo electrodes is comprised by a part of an outer wall of the hydrogengenerator.
 15. A system according to claim 13, wherein one of the twoelectrodes is comprised by a part of an outer wall of one side of thehydrogen generator, and the other of the two electrodes is comprised bya part of an outer wall of the other side of the hydrogen generator, andcomprising an insulator-layer in between the one side and the other sideof the outer wall.
 16. A system according to claim 13, wherein at leastone of the two electrodes comprises an insulator-layer on the surfacethereof.
 17. A system according to claim 16, wherein the insulator-layeris comprised by at least one of the paper, polyolefin such aspolyethylene or polypropylene, polyester such as polyethyleneterephthalate, aromatic or aliphatic polyamide, polyurethane, polyimide,phenol resin, liquid crystalline polymer, PPS, epoxy resin, PEEK, andPES.
 18. A fuel cell system comprising: a power outlet for providingelectrical power for an external device, a module whose internalelectrical or physical property being changed as fuel is used, twoelectrodes installed in the module, for measuring an electrical propertyof a space between the two electrodes, two probe-contacts, each of thembeing contacted with each of the two electrodes electrically, forproviding electrical contact with the two electrodes, and a casing forstoring a fuel to be used for the system, wherein the two electrodes areinstalled in the casing.
 19. A system according to claim 18, wherein oneof the two electrodes is comprised by a part of an outer wall of thecasing.
 20. A system according to claim 18, wherein one of the twoelectrodes is comprised by a part of an outer wall of one side of thecasing, and the other of the two electrodes is comprised by a part of anouter wall of the other side of the casing, and comprising aninsulator-layer in between the one side and the other side of the outerwall.
 21. A system according to claim 18, wherein at least one of thetwo electrodes comprises an insulator-layer on the surface thereof. 22.A system according to claim 21, wherein the insulator-layer is comprisedby at least one of the paper, polyolefin such as polyethylene orpolypropylene, polyester such as polyethylene terephthalate, aromatic oraliphatic polyamide, polyurethane, polyimide, phenol resin, liquidcrystalline polymer, PPS, epoxy resin, PEEK, and PES.
 23. A systemaccording to claim 18, wherein the casing comprises a holding materialto hold the fuel in, and a support member to support the holdingmaterial, and wherein the support member is conductive, and is used asone of said two electrodes.
 24. A system according to claim 23, whereinthe support member has a shape of net, lattice, or is porous.
 25. Asystem according to claim 3, wherein the power outlet and theprobe-contacts are provided on a housing of the fuel cell system.
 26. Anelectronic apparatus used together with a fuel cell system according toclaim 3, the device comprising main probe contacts for electricallyconnecting with said probe-contacts, and a power inlet for electricallyconnecting with said power outlet. 27-51. (canceled)